LiNi₀.₅Mn₁.₅O₄ thin films have been grown by pulsed laser deposition (PLD) on stainless steel (SS) substrates. The crystallinity and structure of thin films were investigated by X-ray diffraction (XRD). Microstructure and surface morphology of the thin films were examined using a field-emission scanning electron microscope (FESEM). The electrochemical properties of the thin films were studied with cyclic voltammetry (CV) and galvanostatic charge-discharge in the potential range between 3.0 and 4.9 V. The electrochemical behavior of LiNi₀.₅Mn₁.₅O₄ thin films showed reversible capacity above 4.7 V and good cycle performance up to 50 cycles.

Abstract The evolutionary role of the so-called “changing-look” (CL) active galactic nucleus (AGN), which is characterized by spectral-type transitions within ∼10 yr, has been suggested in the past few years. By focusing on CL-AGNs having spectra similar to those of broad-line Seyfert 1 galaxies, some authors have proposed that CL-AGNs tend to be at a special evolutionary stage associated with intermediate-to-old stellar populations. Here we attempt to verify this evolutionary role by extending the sample to CL narrow-line Seyfert 1 (NLS1) galaxies, which are believed to be “young” AGNs with a less massive supermassive black hole and high accretion rate. Combining the recent large NLS1 catalog provided by V. S. Paliya et al. and the fifth Sloan Digital Sky Survey (SDSS-V) DR19 spectral survey returns only three CL-NLS1s out of a parent sample of 884 objects, reinforcing the rarity of CL-NLS1s. Subsequent spectral analysis shows that the evolutionary role mentioned above still holds, although CL-NLS1s tend to occupy the young end of the intermediate-old population. Finally, we propose that off-center SDSS spectra caused by the “fiber drop” effect have great potential for determining the properties of the narrow-line region of NLS1s.

Abstract We present photometric and spectroscopic observations of SN 2024abfl, a low-luminosity Type IIP supernova (LLSN) discovered shortly after explosion. The transient reached a peak absolute magnitude of M V = −14.9 and exhibited an extended, flat plateau lasting ∼125 days. From the late-time bolometric light curve, we estimate a 56 Ni mass of ∼0.01 M ⊙ , consistent with other LLSNe. Analytical shock-cooling models fail to reproduce the rapid early rise, indicating that circumstellar matter (CSM) interaction contributed to the initial emission. The spectroscopic evolution is typical of LLSNe, with relatively narrow metal lines and low expansion velocities (≲3000 km s −1 ) that decline slowly over time. We detect a broad “ledge” feature around 4600 Å within 3 days of explosion, which we interpret as a blend of high-ionization, shock-accelerated CSM lines. Multipeaked H α profiles develop during the plateau phase, consistent with complex ejecta–CSM interaction. As one of the best-observed examples of LLSNe, SN 2024abfl exhibits a weak explosion and signatures of nearby CSM, offering new insights into progenitor properties, pre-explosion mass loss, and the diversity of LLSNe.

We report studies of the hydrostatic pressure dependence of the fundamental bandgap of InN, In-rich In1−xGaxN (0<x<0.5) and In1−xAlxN (x=0.25) alloys. The bandgap shift with pressure was measured by optical absorption experiments with samples mounted in diamond anvil cells. The pressure coefficient is found to be 3.0±0.1 meV/kbar for InN. A comparison between our results and previously reported theoretical calculations is presented and discussed. Together with previous experimental results, our data suggest that the pressure coefficients of group III nitride alloys have only a weak dependence on the alloy composition. The photoluminescence signals appear to yield significantly smaller pressure coefficients than the bandgap from absorption measurements. This is due to emission associated with highly localized states. Based on these results, the absolute deformation potentials of the conduction and valence band edges are estimated.

We report an effect that occurs in semiconductors where internal electrical fields interact with a temperature gradient. Steady current vortices and a magnetic field develop in the system, even without external carrier injection. The effect is electrodynamic, energy dissipative, and fundamentally distinct from any previously described electrothermal effects. In bipolar structures the effective thermopower can be significantly modified by the vortices. Joule heating arising from the vortices reduces the thermal conductivity by an amount comparable to the electronic thermal conductivity.

We present results of an optical search for Cepheid variable stars using the Hubble Space Telescope (HST) in 19 hosts of Type Ia supernovae (SNe Ia) and the maser-host galaxy NGC 4258, conducted as part of the SH0ES project (Supernovae and H0 for the Equation of State of dark energy). The targets include 9 newly imaged SN Ia hosts using a novel strategy based on a long-pass filter that minimizes the number of HST orbits required to detect and accurately determine Cepheid properties. We carried out a homogeneous reduction and analysis of all observations, including new universal variability searches in all SN Ia hosts, that yielded a total of 2200 variables with well-defined selection criteria -- the largest such sample identified outside the Local Group. These objects are used in a companion paper to determine the local value of H0 with a total uncertainty of 2.4%.

We report the observation of a current-driven metal (M)-insulator (I) phase oscillation in two-terminal devices incorporating individual WxV1-xO2 nanobeams connected to parallel shunt capacitors. The frequency of the phase oscillation reaches above 5 MHz for approximately 1 mum long devices. The M-I phase oscillation, which coincides with the charging/discharging of the capacitor, occurs through the axial drift of a single M-I domain wall driven by Joule heating and the Peltier effect.

We report on the structural properties and optical and electrical characteristics of InN epitaxial layers grown on highly resistive GaN templates using migration enhanced metalorganic chemical vapor deposition (MEMOCVD). The material quality of InN improved significantly for the layer thickness larger than 150 nm. The highest extracted value of the room temperature electron mobility was close to 850 cm2/V s for samples with electron carrier concentration of ∼4×1018 cm−3. The measured dependence of the electron mobility on electron concentration is interpreted using the model accounting for ionized impurity scattering, polar optical scattering, and compensation. The MEMOCVD-grown material exhibited stronger photoluminescence (PL) compared to InN deposited using conventional metalorganic chemical vapor deposition. Room temperature PL spectra were similar to InN grown using molecular beam epitaxy (MBE) with peak emission at 0.8 eV. The obtained results demonstrate the potential of the MEMOCVD technique for deposition of high quality InN epitaxial layers at reduced temperatures comparable to those used in MBE growth.

We report Raman and time-resolved photoluminescence spectroscopic studies of multiwalled BN and BxCyNz nanotubes. The Raman spectroscopy shows that the as-grown BxCyNz nanotubes are radially phase separated into BN shells and carbon shells. The photoluminescence decay process is characterized by two time constants that are attributed to intra- and inter-BN sheet charge recombination, respectively. A comparison of the photoluminescence of BN nanotubes to that of hexagonal BN is consistent with the existence of a spatially indirect band gap in multiwalled BN nanotubes as predicted by theory.

We have identified a progenitor candidate in archival Hubble Space Telescope (HST) images for the Type Ic supernova (SN Ic) SN 2017ein in NGC 3938, pinpointing the candidate's location via HSTTarget of Opportunity imaging of the SN itself. This would be the first identification of a stellar-like object as a progenitor candidate for any SN Ic to date. We also present observations of SN 2017ein during the first ~49 days since explosion. We find that SN 2017ein most resembles the well-studied SN Ic SN 2007gr. We infer that SN 2017ein experienced a total visual extinction of A_V ≈ 1.0–1.9 mag, predominantly because of dust within the host galaxy. Although the distance is not well known, if this object is the progenitor, it was likely of high initial mass, ~47–48 M⊙ if a single star, or ~60–80 M⊙ if in a binary system. However, we also find that the progenitor candidate could be a very blue and young compact cluster, further implying a very massive (>65 M⊙) progenitor. Furthermore, the actual progenitor might not be associated with the candidate at all and could be far less massive. From the immediate stellar environment, we find possible evidence for three different populations; if the SN progenitor was a member of the youngest population, this would be consistent with an initial mass of ~57 M⊙. After it has faded, the SN should be reobserved at high spatial resolution and sensitivity, to determine whether the candidate is indeed the progenitor.

We show that the band gap bowing trends observed in III-V alloys containing dilute concentrations of Sb or Bi can be explained within the framework of the valence-band anticrossing model. Hybridization of the extended $p$-like states comprising the valence band of the host semiconductor with the close-lying localized $p$-like states of Sb or Bi leads to a nonlinear shift of the valence-band edge and a reduction of the band gap. The two alloys $\mathrm{Ga}{\mathrm{Sb}}_{x}{\mathrm{As}}_{1\ensuremath{-}x}$ and $\mathrm{Ga}{\mathrm{Bi}}_{x}{\mathrm{As}}_{1\ensuremath{-}x}$ are explored in detail, and the results are extrapolated to additional systems.

We report sublimation of crystalline GeTe nanowires at elevated temperatures in vacuum imaged by in situ transmission electron microscopy. The GeTe nanowires exhibit significant melting point suppression in the presence of Au contamination. A nanosized effusion cell is formed by coating the GeTe core with a SiO(2) shell, where the core can be evaporated or sublimated from the open end of the shell at high temperatures. By measuring the speed of the moving interface between the condensed and vapor phases, we determined the vaporization coefficient of these nanowires to be greater than or equal to approximately 10(-3) over a wide range of temperatures. At the final stage of the nanowire vaporization, the material loss occurs at a higher rate, which is evidence of a higher vaporization coefficient for nanosized GeTe. This in situ technique offers a quantitative method of investigating phase transition dynamics and kinetics of nanomaterials, an important topic for designing nanoscale devices to be operated at high temperatures such as phase change memory.

Abstract The effects of applied hydrostatic pressure on the optical transitions in semiconducting single‐walled carbon nanotubes with different diameters and chiralities have been studied using optical absorption and photoluminescence spectroscopy. The excitonic transitions associated with the band‐gap (the first van Hove transition) energies in the carbon nanotubes are found to shift to lower energy at a rate depending on nanotube structure. The excitonic transitions between the first excited confinement states (the second van Hove transitions) are found to be much less sensitive to the applied hydrostatic pressure. All nanotubes show a dependence on their chirality in terms of pressure coefficient of the band‐gap energy, with the larger‐diameter nanotubes exhibiting a higher sensitivity of the band‐gap energy to hydrostatic pressure. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)